Project Summary Aggressive lymphomas associated with HIV infection are often curable with chemotherapy. Chemotherapy failures are much more common in patients with poor performance status, which manifests as advanced stage disease and is typically associated with a delayed diagnosis. The diagnosis of lymphoma in HIV patients is particularly challenging, and often delayed, because the signs and symptoms of lymphadenopathy, fever, night sweats, and weight loss characteristic of lymphoma may also reflect HIV, or opportunistic infections such as tuberculosis (TB). In South Africa, the diagnosis of lymphoma is especially difficult because of the high incidence of TB co-infection, which is the major cause of death in HIV patients. Fine needle aspiration (FNA) is often performed on palpable and enlarged lymph nodes as a front-line diagnostic procedure. The FNA is sometimes suggestive of lymphoma or TB, and is sometimes indeterminate or non-diagnostic. Lymphadenopathy in this setting is so common, and the medical infrastructure to support excisional biopsy and pathology stretched so thin, that definitive excisional biopsies must be prioritized. Those with FNA findings suspicious for lymphoma are sent for excisional biopsy, while others are treated empirically for TB, and only proceed to biopsy if lymphadenopathy is persistent or progressive despite TB treatment. We propose an investigation of molecular markers that may serve as diagnostic adjuncts to improve prioritization for excisional biopsy. The approach involves molecular analysis of immunoglobulin DNA to detect clonal rearrangements in FNA or in plasma specimens. Several studies suggest that circulating tumor DNA can be detected in the plasma of >95% of patients with aggressive B cell lymphomas. We suspect that these rearrangements would also be frequently detected in FNA as well. We propose to study FNA and plasma specimens from 300 HIV patients with lymphadenopathy undergoing FNA for standard clinical indications at the University of the Witwatersrand-affiliated hospitals and clinics in Johannesburg, South Africa. From this group of patients we will identify at least 30 patients with definitive lymphoma (diagnosed by excisional biopsy) and 30 without lymphoma. To make these clinical determinations (lymphoma vs. no-lymphoma), we will follow patients for up to 6 months while standard diagnostic and therapeutic procedures are pursued. When 30 true positive, and corresponding true negative, cases have been identified, we will determine whether clonal immunoglobulin (cIg) DNA is present in FNA, plasma, or both in order to estimate the sensitivity, specificity, positive predictive value and negative predictive value of cIg DNA as a diagnostic adjunct. These studies will also give insight into clonal B-cell proliferations associated with HIV and coinfections. Positive findings from this preliminary study will set the groundwork for a real-time prospective study to determine whether more rapid diagnosis can improve the performance status and long-term disease- free survival of patients with HIV lymphoma.